Commonly assigned U.S. application Ser. No. 07/914,278, filed Jun. 15, 1992, entitled "Low-Voltage, Low-Power Amplifier For Magnetoresistive Sensor" discloses low-noise, low-power, low-voltage amplifier circuits with a single-ended input having no common mode rejection for concurrently biasing and amplifying signals generated by magnetoresistive (MR) sensing elements in a disk storage system. The amplifier circuits comprise a single (grounded) supply voltage source. The head/disk assembly of the disk file is completely enclosed by a highly conductive electrostatically shielded metallic enclosure that operates as a Faraday cage and isolates leads connecting the MR elements with the amplifier circuit from large, fast rise/fall time voltage transients.
These circuits operate very satisfactorily at supply voltages of as low as 4.5 volts. However, there is a need for amplifier circuits having configurations that not only include a single-ended input to eliminate common mode rejection and use a single (grounded) supply voltage, as taught in the application just cited, but also permit operation with supply voltages as low as three volts. This need arises because MR sensors are now being proposed for use with battery-operated low-end storage devices, such as hard disk drives for lap-top and notebook computers. These types of devices require actuator-electronics (AE) modules with extremely low power consumption and supply voltages of less than 4.5 volts.